Enterprise Debug — 4-Phase Systematic Debugging

Philosophy

Bugs are never unique. If it is a bug here, it is a bug elsewhere. The blast radius scan is what separates enterprise debugging from guessing.

Three rules:

1. Find the root cause, not the symptom. A symptom fix creates two future bugs.
2. Scan the blast radius. The same class of bug exists in sibling functions, sibling files, and validation code.
3. Prove the fix with TDD. A fix without a failing test is a guess.

/enterprise-debug order duplication — processOrder called twice in orderHandler.js
/enterprise-debug test failure: userService.test.js "rejects empty email" now fails
/enterprise-debug users report wrong totals on dashboard page

STACK RESOLUTION

Read .claude/enterprise-state/stack-profile.json at skill start. Extract:

• $TEST_CMD = commands.test_all
• $TEST_SINGLE = commands.test_single
• $SOURCE_DIR = structure.source_dirs.backend
• $TENANT_FIELD = multi_tenancy.field
• $FILE_EXTENSIONS = conventions.file_extensions

If no profile exists: BLOCKED — run /enterprise-discover first.

Phase 1: INVESTIGATE (5-15 minutes)

Goal: reproduce the bug, trace the execution path, form a hypothesis.

Step 1: Reproduce

Get the exact error. Not a description of the error — the actual error.

REPRODUCTION
════════════
Trigger:     [exact steps to reproduce — API call, user action, cron job]
Error:       [exact error message, stack trace, or wrong behavior]
Expected:    [what should happen instead]
Frequency:   [always / intermittent / only under specific conditions]
Environment: [dev / prod / both]

If you cannot reproduce, you cannot fix. Spend time here.

For test failures: run the failing test and paste the full output.

$TEST_SINGLE --testPathPattern="<pattern>" --no-coverage 2>&1

For runtime errors: find the error in logs or reproduce via API call.

curl -s http://localhost:3000/api/<endpoint> | jq .

For "wrong data" reports: query the database directly to confirm the data is wrong (not just the display).

SELECT relevant_columns FROM table WHERE conditions;

Step 2: Trace the Execution Path

Follow the data end-to-end. Every layer. No shortcuts.

EXECUTION TRACE
═══════════════
Entry point:  [route/job/webhook that triggers the code]
  → Middleware: [auth, validation — file:line]
  → Route:     [handler function — file:line]
  → Service:   [business logic function — file:line]
  → Query:     [SQL or ORM call — file:line]
  → DB:        [table(s) affected, actual data state]
  → Response:  [what gets returned — file:line]
  → Consumer:  [frontend hook/component — file:line]
  → Render:    [what the user sees — file:line]

Read every file in the trace. Do not skip layers. The bug is often NOT where you think it is.

Step 3: Form a Hypothesis

HYPOTHESIS
══════════
I think: [specific root cause]
Because: [evidence from the trace — cite file:line]
This predicts: [if I'm right, then X should also be true]
Verification: [how to test the hypothesis — a query, a log check, a test]

Run the verification. If the hypothesis is wrong, form a new one. Do not proceed to Phase 2 until the hypothesis is verified.

Step 4: Find Working Examples

Search for similar code that works correctly. This reveals what the buggy code is missing.

# Find functions doing the same operation that work correctly
grep -r "similar_pattern" $SOURCE_DIR/ --include='*.$FILE_EXTENSIONS' -l

Compare the working version with the broken version. The difference is often the fix.

Phase 2: BLAST RADIUS SCAN (5-10 minutes)

This phase is MANDATORY. Do not skip it. Do not abbreviate it. The blast radius scan is the single highest-value activity in debugging.

2a: Same-File Siblings

If the buggy function belongs to a group of similar functions in the same file, check EVERY sibling.

SAME-FILE SIBLINGS: [file path]
═══════════════════
Buggy function: [name] — line [N]
Bug class:      [what category of bug — missing filter, wrong column, no null guard, etc.]

Sibling 1: [function name] — line [N]
  Has same guard/filter? [YES / NO — SAME BUG]

Sibling 2: [function name] — line [N]
  Has same guard/filter? [YES / NO — SAME BUG]

... (list ALL siblings, not "a few")

Example: If searchSuppliers() is missing a WHERE is_active = true filter, check searchOrders(), searchProducts(), searchCustomers() — every search function in the same file.

2b: Cross-File Siblings

Search the ENTIRE module/service directory for functions doing the same logical operation.

# Find all functions with similar names
grep -rn "function.*Staff\|getStaff\|staff.*query\|staff.*list" $SOURCE_DIR/services/ --include='*.$FILE_EXTENSIONS'

# Find all functions with similar SQL patterns
grep -rn "SELECT.*FROM.*staff\|FROM.*users.*WHERE" $SOURCE_DIR/ --include='*.$FILE_EXTENSIONS'

# Find all files in the same service directory
ls $SOURCE_DIR/services/<module>/

CROSS-FILE SIBLINGS
════════════════════
Bug class: [what to search for]

Match 1: [function name] in [file:line]
  Does same logical operation? [YES / NO]
  Has same guard/filter?       [YES / NO — SAME BUG]

Match 2: [function name] in [file:line]
  Does same logical operation? [YES / NO]
  Has same guard/filter?       [YES / NO — SAME BUG]

... (list ALL matches from grep scan)

2c: Validation and Consumer Functions

Find every function that consumes or validates the same data.

# Find consumers of the affected data
grep -rn "variable_name\|function_name" $SOURCE_DIR/ --include='*.$FILE_EXTENSIONS'

CONSUMERS & VALIDATORS
══════════════════════
Data source: [function that produces the data]

Consumer 1: [function/component name] in [file:line]
  Purpose:  [what it does with the data]
  Affected by bug? [YES — needs fix / NO — different data path]

Consumer 2: [function/component name] in [file:line]
  Purpose:  [what it does with the data]
  Affected by bug? [YES — needs fix / NO — different data path]

Validator 1: [function name] in [file:line]
  Enforces same constraints? [YES / NO — MISSING GUARD]

2d: Edge Cases

For each bug, systematically check boundary conditions:

EDGE CASES
══════════
Empty/null input:           [OK / BUG — describe]
Zero-length array:          [OK / BUG — describe]
Inactive/deleted records:   [OK / BUG — describe]
System/service accounts:    [OK / BUG — describe]
Permission boundaries:      [OK / BUG — describe]
Different entry points:     [OK / BUG — describe]
  - API route:              [OK / BUG]
  - Internal service call:  [OK / BUG]
  - Cron/background job:    [OK / BUG]
Concurrent execution:       [OK / BUG — describe]
Very large input (10K+):    [OK / BUG — describe]
Unicode/special characters: [OK / BUG — describe]

Blast Radius Summary

BLAST RADIUS SUMMARY
════════════════════
Same-file siblings checked:  [N] — [N] with same bug
Cross-file siblings checked: [N] — [N] with same bug
Consumers/validators:        [N] — [N] affected
Edge cases checked:          [N] — [N] bugs found

Total additional bugs found: [N]
All findings become postconditions in Phase 4.

Phase 3: ROOT CAUSE (2-5 minutes)

Identify the Single Root Cause

The root cause is ONE thing. Not "multiple issues" — one thing that, when fixed, resolves all manifestations.

ROOT CAUSE
══════════
What:  [the specific defect — e.g., "missing WHERE is_active = true in getStaffUsers query"]
Where: [exact file:line]
Why:   [how it got there — copied from a function that didn't need the filter,
        original author didn't consider inactive users, etc.]
When:  [when it was introduced — git blame if useful]

Verification: fixing this one thing fixes ALL of the following:
  1. [original bug report symptom]
  2. [blast radius finding 1]
  3. [blast radius finding 2]
  ...

Verify the Root Cause

Ask: "If I fix ONLY this one thing, does every manifestation resolve?"

• YES: proceed to Phase 4.
• NO: you found a symptom, not the root cause. Go deeper.

The Circuit Breaker (NON-NEGOTIABLE)

Track your fix attempts — persisted in JSON so the count survives context compression:

# Read current fix attempt count
node -e "
  const fs = require('fs');
  const f = '.claude/enterprise-state/<slug>.json';
  try {
    const s = JSON.parse(fs.readFileSync(f));
    s.circuit_breakers.debug_fix_attempts++;
    console.log('Fix attempt:', s.circuit_breakers.debug_fix_attempts, '/', s.circuit_breakers.debug_max);
    if (s.circuit_breakers.debug_fix_attempts >= s.circuit_breakers.debug_max) {
      console.log('>>> CIRCUIT BREAKER TRIGGERED <<<');
    }
    fs.writeFileSync(f, JSON.stringify(s, null, 2));
  } catch(e) {
    console.log('No pipeline state file — tracking manually');
  }
"

FIX ATTEMPTS (also persisted in .claude/enterprise-state/<slug>.json)
═════════════
Attempt 1: [what you tried] — Result: [still broken because...]
Attempt 2: [what you tried] — Result: [still broken because...]
Attempt 3: [what you tried] — Result: [still broken because...]

>>> CIRCUIT BREAKER TRIGGERED <<<

If 3 fix attempts fail: STOP. Do not try fix #4. Instead:

1. Question the architecture. The bug may be a design problem, not a code problem.
2. Widen the investigation. You may be looking at the wrong layer entirely.
3. Ask for help. Describe what you've tried and why each attempt failed.
4. Consider rewriting. If the code is unmaintainable, a targeted rewrite may be cheaper than a 4th patch.

The circuit breaker exists because fix-forward loops are the most expensive failure mode in debugging. Each failed attempt adds complexity, introduces regression risk, and burns context. Three attempts is the limit.

Phase 4: FIX — TDD (5-20 minutes)

Every bug fix follows the TDD sequence. No exceptions.

Step 1: Write the Reproduction Test

Write a test that proves the bug exists by asserting the WRONG behavior.

// Example: bug is that getStaffUsers returns inactive users
test('BUG REPRODUCTION: getStaffUsers currently returns inactive users', async () => {
  // Setup: create an inactive user
  // Act: call getStaffUsers
  // Assert: inactive user IS in the result (proving the bug exists)
  const result = await getStaffUsers(tenantId);
  const inactiveUser = result.find(u => u.id === inactiveUserId);
  expect(inactiveUser).toBeDefined(); // This PASSES — bug exists
});

Step 2: Run the Test — Watch it PASS

$TEST_SINGLE --testPathPattern="<pattern>" --no-coverage 2>&1 | tail -20

The test MUST pass. This proves the bug is real and the test catches it.

Step 3: Invert the Assertion

Change the test to assert the CORRECT behavior.

test('getStaffUsers excludes inactive users', async () => {
  const result = await getStaffUsers(tenantId);
  const inactiveUser = result.find(u => u.id === inactiveUserId);
  expect(inactiveUser).toBeUndefined(); // This FAILS — fix not applied yet
});

Step 4: Run the Test — Watch it FAIL

$TEST_SINGLE --testPathPattern="<pattern>" --no-coverage 2>&1 | tail -20

The test MUST fail. This proves the test will catch regressions.

Step 5: Write the Fix

Fix the root cause identified in Phase 3.

Step 6: Run the Test — Watch it PASS

$TEST_SINGLE --testPathPattern="<pattern>" --no-coverage 2>&1 | tail -20

The test MUST pass. The bug is fixed.

Step 7: Blast Radius Postconditions

Every finding from Phase 2 becomes a test:

POSTCONDITION MAPPING
═════════════════════
Root cause fix:
  PC-1: [original bug] → test: "[test description]"

Same-file siblings:
  PC-2: [sibling 1 fix] → test: "[test description]"
  PC-3: [sibling 2 fix] → test: "[test description]"

Cross-file siblings:
  PC-4: [cross-file fix] → test: "[test description]"

Edge cases:
  PC-5: [null input handling] → test: "[test description]"
  PC-6: [inactive user handling] → test: "[test description]"

Consumer verification:
  PC-7: [consumer 1 gets correct data] → test: "[test description]"
  PC-8: [consumer 2 gets correct data] → test: "[test description]"

Write each test following the same RED-GREEN sequence (steps 3-6).

Step 8: Run Full Suite

$TEST_CMD --no-coverage 2>&1 | tail -30

All tests must pass. Zero regressions.

Step 9: Commit

git add -A && git commit -m "fix: [root cause description]

Blast radius: [N] sibling bugs fixed, [N] edge cases covered
Tests: [N] new tests, [N] total passing"

Output — Debug Report

Print this as your final output after the fix is verified:

═══════════════════════════════════════════════════════════
                    ENTERPRISE DEBUG REPORT
═══════════════════════════════════════════════════════════

## Bug
[1-2 sentence description of the bug as reported]

## Root Cause
[1-2 sentences — the actual defect, not the symptom]
File: [file:line]

## Investigation Trace
Entry → [layer] → [layer] → [layer] → ROOT CAUSE at [file:line]

## Blast Radius
Same-file siblings:   [N] checked, [N] had same bug
Cross-file siblings:  [N] checked, [N] had same bug
Consumers/validators: [N] checked, [N] affected
Edge cases:           [N] checked, [N] bugs found
Total additional bugs found: [N]

## Fix
Files changed: [list]
  [file 1]: [what changed and why]
  [file 2]: [what changed and why]

## TDD Evidence
  PC-1: [description] — RED at [time] → GREEN at [time]
  PC-2: [description] — RED at [time] → GREEN at [time]
  ...
  Tests: [N] new, [N] total passing, 0 failing

## Fix Attempts
  Attempts: [N] (limit: 3)
  Circuit breaker: [not triggered / triggered at attempt N]

## Prevention
  [How to prevent this class of bug in future — pattern to follow,
   lint rule to add, guard to standardize]

═══════════════════════════════════════════════════════════

Quick Reference — When to Use Each Phase

Anti-Patterns — Things That Feel Productive but Waste Time